Refrigerating system



Patented Aug. 27, 1940 v UNITED STATES REFRIGERATING SYSTEM No Drawing.Application October 25, 1939, Serial No. 301,228

Claiins.

A. This invention relates to processes of refrigeration for systemscontaining iron and copper parts and utilizing a halogenated hydrocarbonrefrigerant.

B. In refrigerating systems which use halogenated hydrocarbons such asmethyl chloride and dichlorodifiuoromethane as refrigerants a phenomenonis observed which is called copper plating. Parts of the system whichare made of non-cuprous metals, notably the moving parts such as pistonsand valves, become coated with a layer of copper. This coating mayproceed to the point where the efiiciency of the apparatus is materiallydecreased or tothe point where the 16 apparatus may be unable tofunction. In these systems mineral oil is generally used as a lubricantand it has been observed that much of the plating occurs on the portionsof the apparatus which need lubrication or which are in constant 20contact with the lubricant. This has led to the Y theory that copperfrom the tubes or otherportions of system, which are formed of thatmetal or of alloys thereof, is dissolved or suspended in the lubricant,or mixtures of the lubricant and refrigerant, and deposited on thoseparts.

C. Regardless of the manner in which itoccurs, however, it is an objectof this invention to inhibit copper plating in refrigerating systems ofthe type described.

= D. The objects of the invention-are accomplished, generally speaking,by including in the system a.small amount of picolinic acid. Thepicolinic acid can be added with successful results to the lubricatingoil which is used in the system. E. Although the manner in whichpicolinic acid functions as an inhibitor of copper-plating is notclearly understood, it is thought that the copper in the parts ofrefrigeration systems constructed of this metal, forms a chelatecompound with picolinic acid producing a relatively insoluble, adherentfilm on the metallic surface. The plating of the copper from therelatively small amount of the complex that may be in solution isprobably prevented by the formation of a similar chelate iron complex onthe iron and steel surfaces where the plating would normally occur inthe absence of picolinic acid. However, the applicants do not wish to bebound by any 50 particular theory of operation.

F. The following example illustrates, but does not limit the invention;the plcolinic acid being used in any amount which is necessary toproduce optimum results.

Example od of time which is suflicient to produce objectionable copperplating in systems not containing picolinic acid and it was found thatcopper plating had been entirely prevented. It has been demonstratedthat additions of picolinicacid from 0.05% to 1.0% based on the weightof the lubricant employed are suflicient to inhibit or to totallyprevent copper plating.

'G. Although copper plating has occurred in household and someindustrial refrigerating units, it has been more bothersome in largeunits employing heavy duty compressors. This has to some extent reducedthe application of halogenatedhydrocarbon refrigerants in the heavy dutyfield. By this invention the objection to halogenated hydrocarbonrefrigerants in the heavy duty field is removed.

H. As many apparently widely different embodiments of this invention maybe made without departing from the spirit and scope thereof, it is to beunderstood that we do not limit ourselves to the specific embodimentsthereof except as defined in the appended claims.

We claim:

1. A process of refrigeration which comprises condensing and evaporatinga, halogenated hydrocarbon in the presence of a mineral oil containingpicolinic acid. a

2. The process of claim 1 in which the mineral oil contains from 0.05%to 0.1% of pieolinic acid.

3. The process of claim 1 in which the mineral lubricating oil containsabout 0.1% of picolinlc acid.

4. A refrigerating system containing. iron parts, copper parts, ahalogenated hydrocarbon refrigerant, a lubricating oil, and picolinicacid.

5. The method of inhibiting copper plating in a refrigerating systemcontaining a halogenated hydrocarbon refrigerant which comprises addingpicolinic acid to the system.

FREDERICK B. DOWNING. WILLIAM H. MARKWOOD, JR.

